Method of truing the peripheral surfaces of band saw wheels



Feb. 10, 1953 M. H. MATER ETAL METHOD OF TRUING THE PERIPHERAL SURFACES OF BAND SAW WHEELS Filed June 1, 1948 aw 5 J MM m f A M 0 M M 4 ma fi M Patented Feb. 10, 1953 OFFICE METHOD OF TRUING THE PERIPHERAL SURFACES OF BAND SAW WHEELS Milton iii. Mater and Claud C. Walker, SR2, Corvallis, Oreg.

I Application June 1, 1948, Serial No. 30,444

1 Claim. 1

Our present invention relates to a method and means for truing the peripheral surfaces of bandsaw wheels or similar rotating bodies such as calender rolls and paper drying rolls. The invention has its greatest utility in truing the surfaces of bandsaw Wheels, since a great deal of wear is imposed upon such wheels and the need for true surfaces is acute. Heretofore it has been the practice in bandsaw mills to slow their wheels to approximately one-third of their normal speed while grinding the wheels. In mills driven directly by electric or internal combustion engine power, this is an expensive process, involving the use of separate slow speed motors or engines and/or pulleys and belts; also it involves using many man-hours of skilled millwright labor to install and then dismantle this slowing down setup. In fact, in the smaller bandsaws used in remanufacturing lumber, it is often the practice to remove the wheels and carry them to a machine shop where they are turned on special machines. The principal object of our invention is to simplify the process of truing up band wheels, so that it is no longer a costly maintenance operation.

Attempts have been made in the past to grind bandsaw wheels running at full speed. These attempts have always been unsatisfactory and highly dangerous because of the high speeds involved, a bandsaw wheel usually operating at peripheral speeds in the range of 9,000 to 10,000 feet per minute. At such speeds a grindstone or grinding block is subject to excess overheatin and tremendous pressures, with the result that the grinding member becomes overheated and cannot perform its work, and in various experimental attempts has flown to pieces with resulting injuries to the operator. For these reasons the present practice in bandsaw mills is to shut down the mill and grind the surfaces of the wheels at low speeds. Our invention permits the grinding of the wheels while the wheel is running at high speed.

By previous methods involving slowing the wheels to low speeds, the grinding of the wheel has heretofore required a total elapsed time of from six to twelve hours for a nine-foot wheel, whereas with our invention the total elapsed time for grinding a nine-foot wheel is in the neighborhood of three hours. When it is considered that the wages of skilled millwrights and saw filers are very high and theloss of time of the mill results in much higher losses to the operator, it will be seen that our invention results in a tremendous saving to the mill owner.

The present invention comprises an improve? ment in shear grinding wherein the surface is trued by a non-motorized rotary grindstone contacting the surface of the wheel along a peripheral edge, with the axis of rotation of the grindstone being inclined to the surface of the wheel. Attempts have been made in the past to shear grind wheels running at full speed by means of a grindstone whose axis of rotation is not only inclined to the surface of the wheel but inclined to the plane of the wheel so that a component of force is imparted to the grindstone, causing it to revolve about its axis. Such attempts hav met with failure since the grindstone does not remove metal under these conditions, and more often than not thegrindstone flewlto pieces. In order to grind the wheel and prevent dangerous destruction of the grindstone, it is necessary to slow the wheel being trued down to approximately 3,000 feet per minute, with the consequent expensive installations, while the mill was shut down so that the bandsaw wheels could be operated at these slow speeds. Attempts have also been made to true wheel surfaces or the like by shear grinding using a rotary grindstone driven by an electric motor at speeds normally encountered in such motors, i. e. in the range of 1,200 to 1,800 R. P. M. Such attempts always fail, since the surface of the wheel is glazed or the grindstone flies apart.

Our invention not only permits of a saving in time, since the total elapsed time is short and the grinding may be accomplished while the wheels are turning at full speed, but also results in a saving due to the lesser wearing of the grindstone resulting therefrom. The best operation known on a nine-foot wheel under previous conditions wore out two complete grinding stones five inches in diameter, whereas when using our invention a single five-inch grindstone will be only about half-worn. V

The objects and further advantages of the present invention will be more readily ascertained from inspection of the following specification taken in connection with the accompanying drawings wherein like numerals refer to like parts throughout, while the features of novelty will be more distinctly pointed out in theappended claim.

In the drawings: a 1

Fig. 1 is a view taken froma side of a bandsaw wheel showing aportion of the wheel, and show-'- ing the machine of the present invention in operation thereon, portions of the machine being broken away to illustrate details thereof;

Fig. 2 ls--a 'plan view of the machine of the i present invention;

saw mill with the machine of the present invention shown in operation on both of the bandsaw wheels;

Fig. 4 is a schematic front view of the lower bandsaw wheel showing the rotary grindstone in one angular relation to the plane of the wheel wherein the peripheral movement of the portion of the grindstone in contact with the wheel is in the direction opposite to the direction of movement of the Wheel; and

Fig. is a view similar to Fig. 4 showing the grindstone in a different angular relation wherein the grindstone movement is in the same direction as the movement of the wheel.

A bandsaw mill usually comprises a supporting structure It in which is located a pit or well II. A bandsaw frame I2 is mounted in the pit and supports transverse shafts l3 and I4 forming the axles of the lower bandsaw wheel [5 and the upper bandsawwheel I5, respectively. A bandsaw i1 is trained about the two wheels and driven at high speedthereby. A carriage I8 is reciprocated alon side of the pit II and supports the log to with an edge overhanging the pit and in position to be engaged by the bandsaw so that cants and slabs may be sliced from the log. The cant or slab topples onto live rolls (not shown) which transport it from the vicinity of the saw while the carriage is moved back and the log shifted for another cut.

The machine of thepresent invention comprises a pair of supporting angle bars 25 which are adapted to be mounted horizontally in spaced relation uponthe flanges of structural members 26 which may be welded orotherwise aiiixed to the base of-the bandsaw frame at each side of the upper portion of the periphery of the lower band wheel 15, the angle bars being attached by means of bolts 21. A pair of small bracket plates 28 are fixed'to the angle bars at each end and support alignment screws ZQ-"eng'aging the ends of supporting plates 39, each of which supports a pivot bolt 3| or the like. A cradle is pivotally mounted upon the pivot bolt 3!, the cradle comprisin end plates 32 and longitudinal guiding means such as rods 33. Each of the'plates 32 is provided with a limiting pin 34 which projects through an arcuate slot 35 concentric with the axis of the pivot bolts 3| and extending approximately sixty degrees beyond each side of the vertical. A longitudinal traversing screw 3l-is rotatably mounted in the; plates 32 and fixed to a hand wheel 38 located outside of one of the plates 38. The guide rods33 pass through guiding lugs 39' depending from a carriagedn' which isprovided with a threaded lug-l threadedly engaging the longitudinaltraversing screw-3l whereby rotation of the hand wheel 38. causes-movement o-f'the carriage longitudinallyof-the cradle. The carriage 40 co'mprisesa baseplate having a pair of guide flanges 42 thereon comprising transverse guiding means such-as guideways 43. A slide 4'4 is retained in the guideways 43 and is provided with a threaded depending lug 45 threadedly engaging a transverse feed screw 3 3 rotatably mounted in lugs 47 on the base ofthe carriage 40, the screw being provided-with a hand wheel 48 whereby rotation of the screw causes transversemovement of the slide 44. A pivot stud 50 projects vertically upward from the slide 44 through an opening in a'inotor mounting plate 5| supported by'the slide. An-electric motor 52 is mounted upon the motor mounting plate as by means of bolts 53 which do not. project below the surfaceofthe-motor mountingplate. The motor 52 is preferably of the gear reduction type having a built-in reduction gear box 55 at the forward end thereof from which projects a driven shaft 56. A rotary grindstone 51 is coaxially mounted upon the shaft 56 by any suitable means. The grindstone could be solid, but we prefer the cup type since the shape thereof is conducive to rapid removal of heat from the grinding surface.

The cradle as a whole may be tilted about the pivot bolts 3| until the limiting pin 34 strikes the end of slot .35. The weight of the motor tends to .hold the .cradlein the tilted position, but we prefer clamping the cradle in this position by tightening the bolts 3! so as to prevent chattering. The hand wheel 48 is rotated until the grindstone 51 contacts the surface of the wheel I5. Thereafter as the peripheral edge of the grindstone wears away the hand wheel 48 is turned by the operator to cause rotation of the transverse feeding screw 45 so that a constant pressure is exerted on the surface of the wheel to be truedQ As seen in Fig. 3, the machine is so arranged that the axis of revolution of the grindstone 51 is in the prolongation of a chord preferably intersecting a normal radius at about its midpoint so that the end face of the grindstone lies in a plane of about'thirty degrees to the surface of the wheel. The motor mounting plate 5| is held in fixed position relative to the slide 44 by a nut 58 threaded on the stud 5! If the axis of the grindstone is so located as to be parallel to the plane of the wheel, as seen in Fig, 1, the grinding motion will be substantially transverse to the plane of the wheel. If, however, the motor mounting plate M is shifted so as to dispose the axis of the grindstone at an inclination to the planeofthe wheel, as seen in Fig. 4, the-working portion of the edge of the grindstone will bemoving in a direction contrary to the'direction of movement of the surface of the wheel. If the axis is shifted in the opposite direction, as seen in Fig. 5,th-e working portion will be moving in the same direction as the surface of the wheel.

In the operation of 'truing a wheel, we have found that it is necessary to reduce the normal speed of the-electric motor, which is generally in the range of -l200 to 1800 R. P. M, to slower speeds so that-the peripheral speed of the grindstone would be in the range of to 1109 feet per minute; preferably below 150 feet; per minute, such reduction being accomplished through the reduction gearing in the reduction gear head 55.

With a' bandsaw wheel or a similar rotating :1 and 8.2 l."- The relatively-slow rotation of the grindstonecauses increments of the working surface of the grindstone constantly to shift from working to non-working position, thus permitting the grindstone to coolitselfand causing the fine particles ofgrit and chips from the wheel to be shaken loose from the pores of the grindstone. The grindstone is moved bodily parallel to the surface of the wheel by turning the hand wheel 33; such movement being controlled-by a skilledgrinder.

We have found that maintaining tlieaxis of the grindstoneparallel to the plane of the wheel. as illustrated in Fig; 1,'while rotating the grind stone at a slow relative surface speed with respect to the surface speed of the wheel, will result in efficient rough grinding of the surface If, however, the axis of the grindstone is angularly shifted to cause a positive relative movement, as seen in Fig. 4, the grinding action will be accomplished a little faster, and rough grinding is preferably done while the grindstone is so shifted. Shifting the grindstone to produce negative relative movement will reduce the grinding action, and the finer finish grinding is preferably accomplished while the grindstone is so shifted. With a nine-foot bandsaw wheel operating at 10,000 feet per minute and a five-inch grindstone operating at 500 feet per minute, the positive relative grinding movement may be accomplished at speeds in the range of 10,300 to 10,500 feet per minute, when the grindstone is shifted as seen in Fig. 4; and the negative relative speed may be in the order of 9,500 to 9,700 feet per minute when the grindstone is shifted as seen in Fig. 5. The grindstones are very little worn in comparison with previous experience along this line, they are never shattered or exploded, the wheel surface is never glazed, and exact trueness is achieved in a minimum length of time.

In utilizing the grinding mechanism in a bandsaw mill, a vertical shield 90 is built in the space between the upper and lower bandsaw wheels close to the saw to protect the operator from accidentally falling into the saw or moving one of his limbs into the saw accidentally while grinding. The shield 69 may be mounted upon the angle bars 26 and its upper end will support the outer ends of spaced angle bars 6| suitably braced to the frame of the machine to provide a support for the angle bars 25 when the machine is lifted to contact the lower surface of the upper wheel IS. The same principle may be put into operation by canting the cradle until the pins 34 contact the opposite limit of the limiting slot 35. If desired, the cradle may be reversed end for end so that the end face of the grindstone faces the oncoming portion of the upper band wheel, as was the case when the grinding of the lower band wheel is accomplished. However, either direction of movement relative to the grindstone is permissible and permitted by practicing our method and utilizing our machine.

Having illustrated and described a preferred embodiment of the invention, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. We claim as our invention all such modifications as come within the true spirit and scope of the appended claim.

We claim:

The method of truing the peripheral surface of a band saw wheel of large diameter and comprising a rim and radial supporting means secured to portions of said rim with other portions thereof being radially free whereby centrifugal force effects distortion of the peripheral surface of said rim, comprising rotating the wheel to be trued at a high peripheral speed in the order of thousands of feet per minute approximating the peripheral speed of the wheel in use, contactin the distorted portions of the peripheral surface of said wheel with a peripheral edge of a relatively small grinding wheelwhose axis of revolution is inclined with respect to the peripheral surface of the wheel at the point of contact and inclined with respect to aplane normal to the axis of the wheel, positively driving said grinding wheel at a relatively low peripheral speed in the order of hundreds of feet per minute, and maintaining the foregoing relative conditions and positions while grinding off the distorted areas of the peripheral surface of the rim during movement of the grinding wheel bodily parallel to the axis of rotation of the wheel whereby to remove surface portions of the rim until the peripheral surface of the wheel to be trued is a true cylinder while rotating at its approximate speed of use.

MILTON H. MATER. CLAUD C. WALKER, SR.

- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,394,704 Barnhart Oct. 26, 1921 1,806,226 Voegel May 19, 1931 2,023,347 Van Dec. 3, 1935 2,115,908 Fox May 3, 1938 2,156,485 Thyssen May 2, 1939 2,220,768 Indge Nov. 5, 1940 

